Assuming a dead level surface and away from obvious magnetic interference (loudspeaker magnets, running motors, large power lines, etc.) I have a handful of questions about suitable locations for doing an IMU calibration:

1) Can it be done indoors?
2) What sort of distance should you put between the UAV and, say, a metal object the size of a car?
3) How about the size of a manhole cover?
4) Re-bar contained in a driveway or sidewalk?
5) If done outside, how much wind can be put up with while calibrating the IMU?

Thanks for any help.  You see where I am headed with this...and if I have left off a couple of scenarios that I am sure to run across, please let me know.

DGH

Dg,

No scientific data but my experience with many successful IMU calibrations.

1) Can it be done indoors?
I do mine indoors, on a solid oak table, I shim the legs and insure that my props are level to the world with a level and a pane of glass spanning the props. I usually do it when nobody is home and try to be perfectly still. I also have started putting the bird in the fridge (Battery and SD card removed) for about five minutes before doing it. Seems to solve the slow "warming Up" issue. I have everything in place and running (controller, tablet, app) so I can proceed with the cal as soon as I bring it in from the fridge. (some seem concerned about condensation but I haven't experienced any issues)

2) What sort of distance should you put between the UAV and, say, a metal object the size of a car?
I don't know the answer but I'd sure stay far away from something like that, maybe 50' or better at a minimum?

3) How about the size of a manhole cover?
I'd still stay as far away as I could of any metal objects

4) Re-bar contained in a driveway or sidewalk?
No, I would not do it on a concrete surface that contains rebar or any other metals. When I did my first few I was doing it on my granite countertop and someone chimed in and said that many forms of granite contain metals, so I don't even do it on the granite anymore.

5) If done outside, how much wind can be put up with while calibrating the IMU?
I don't think I'd feel real comfortable doing it outside unless it was relatively still and I had a wood table or something to level it on.

Don't know if that will help or not but that's been my experience. I'm sure others will chime in with their skill, experience and opinions.

Good luck!

Jerry

JtrJr-UAV Pilot Posted at 2015-6-25 03:36
Dg,

No scientific data but my experience with many successful IMU calibrations.

Is metal an issue with calibrating the IMU or just the compass?

Rigworker Posted at 2015-6-25 04:56
Is metal an issue with calibrating the IMU or just the compass?

Rig,

As far as I know, both. Again, I'm a little out of my comfort zone saying these things with any certainty. I'm basing my answers on what I've read and learned from others that have much more knowledge about these things than I do. Maybe someone with a better understanding of "why" will chime in.

Jerry

JtrJr-UAV Pilot Posted at 2015-6-25 05:04
Rig,

As far as I know, both. Again, I'm a little out of my comfort zone saying these things with  ...

I thought the IMU was gyroscopes and acceleration sensors.  Metal shouldnt bother them. Dont get me wrong, I do all of the calibrations away from metal and electronics. I was just curious.

Rigworker Posted at 2015-6-25 05:16
I thought the IMU was gyroscopes and acceleration sensors.  Metal shouldnt bother them. Dont get m ...

Rig,

Not trying to be short but I don't think I could have been any clearer with "Maybe someone with a better understanding of "why" will chime in." Many people are on the job right now, I'm retired, just thought I'd throw my two cents in just in case the OP was trying to get it done now. Better to err on the side of caution and keep it away from metal.

Jerry

Jerry

JtrJr-UAV Pilot Posted at 2015-6-25 06:14
Rig,

Not trying to be short but I don't think I could have been any clearer with "Maybe someone w ...

I believe I reiterated your comment about staying away from metal to be safe.

Rigworker Posted at 2015-6-25 06:19
I believe I reiterated your comment about staying away from metal to be safe.

Rig,

It's all good! Hopefully someone in the know will pop in.

Jerry

Dg & Rig,

I kind of felt like I was being a bit lazy so I went out and searched out the advanced IMU calibration. I'm not finding any information that confirms that you have to be careful with metal around when doing the calibration. As Rig noted the compass is a different component and the IMU is actually part of the NAZA module. I'm still going to be very careful just out of caution but unless someone else chimes in with more technical experience I'd say the bird being as level and still as possible is the greater issue. The DJI Mr. Mat video wasn't very helpful but I did come across this Phantom 3 video which I thought was quite good. Not really directed just at the IMU but the items in the DJI Pilot software.  I think it was previously posted but it can't help to re-post the link. Sorry if I caused any confusion.

Jerry

JtrJr-UAV Pilot Posted at 2015-6-25 09:09
Dg & Rig,

I kind of felt like I was being a bit lazy so I went out and searched out the advanced IM ...

Jerry,
Nice work! Obviously I am the lazier of us two ;-) I found a couple youtube videos that speak about the IMU on different drones. They do not mention anything about metal either. As both of us have mentioned before, it is better to err on the side of caution. I do all calibrations well away from any metal, electrical or magmetic areas.
Better safe than sorry.